The present invention relates to an injection element for a combustion component that runs on two propellants, having a first, central injection channel which can be connected to a first propellant supply for a first propellant, and having a second injection channel which annularly surrounds the first injection channel, and can be connected to a second propellant supply for a second propellant.
An injection element for a combustion component running on two propellants is described, for example, in U.S. Pat. No. 5,660,039. The injection element includes a first, central injection channel, which can be connected to a first propellant supply for a first propellant, and a second injection channel, which annularly surrounds the first injection channel and which can be connected to a second propellant supply for a second propellant. The injection element is a bicoaxial injection element, a tricoaxial injection system being formed after installing the injection element in an injection nozzle, through a space, which is between an injection wall that acts as a front panel and the injection element. Therefore, there is no rigid connection between the faceplate and the injection element.
However, such a system can, at best, be used in small combustion chambers, e.g., gas generators, where it is not absolutely necessary to reinforce the faceplate. In the case of larger combustion chambers, such as main combustion chambers of rocket engines, the entire surface of the faceplate must be reinforced.
Therefore, one object of the present invention is to provide an injection element, as well as an injection head, which have a high mechanical stability, allow effective combustion, and can be used universally.
The present invention provides an injection element, which, in contrast to the bicoaxial injection elements described above, is in the form of a tricoaxial injection element. This arrangement provides an injection element having three propellant streams, all three of which are arranged coaxially. The injection element is designed to be used in a combustion component, such as a rocket combustion chamber, which runs on two propellants (both of which can be liquid, gaseous, or a gas-liquid mixture). The injection element has a first, central injection channel, which can be connected to a first propellant supply for a first propellant, and a second injection channel, which annularly surrounds the first injection channel and which can be connected to a second propellant supply for a second propellant.
The present invention provides for the injection element having a third propellant channel, which annularly surrounds the second propellant channel and which is in fluid communication with the first injection channel. Therefore, the injection element includes a tricoaxial design.
This arrangement allows previously utilized injection-head designs to be used or retained for this injection element having three propellant streams, whereby the use of the injection element is considerably simplified. The injection head does not have to be specially adapted. In addition, these injection elements allow the faceplate to be fastened to the injection-head base plate, since no gaps must remain between the faceplate and the injection element. All three propellant streams are formed inside the injection element so that the number of elements can be easily scaled to the respective application. Dividing up the first propellant into two streams, through the central injection channel, and through the external, annular injection channel inside the injection element, improves the control and testability of an individual injection element. In addition, this arrangement considerably reduces the accuracy requirements for the faceplate. The geometrical accuracy required for the injection system to function may be more easily produced for the component parts of the injection element.
In addition to all these advantages of the present invention, it is ensured that the injection elements may be operated at a high mass flowrate per injection element, in order to reduce the number of injection elements, and therefore, to reduce the costs of manufacturing and installation, as well as integration. Furthermore, the tricoaxial injection ensures an improved propellant atomization, since two parallel shear surfaces are produced between the injected propellant streams, between the central stream and the internal annular stream, as well as between the internal and external annular streams.
In one embodiment of the present invention, the third injection channel is connected to the first injection channel via flow channels. These flow channels allow the division of the propellant streams between the third injection channel and the central, first injection channel, to be controlled by the number and size of the injection channels, which can be matched to the pressure difference between the first and third injection channels. The division of the propellant streams may also be subsequently modified by adding additional flow channels or by closing flow channels.
In particular, the flow channels may be embedded in connecting elements, which penetrate the second injection channel. Thus, the connecting elements may, for example, be in the form of cross-pieces, which subdivide the annular, second injection channel into several annular sectors, at least over a segment of its length, in the flow direction of the second propellant.
The flow channels may have different shapes and may extend to the first injection channel in different ways. The flow channels may extend radially to the longitudinal extension of the first injection channel, in the direction of the first injection channel, which, generally represents the shortest possible connection to the first injection channel. However, the flow channels may also extend at an angle to the flow direction of the second propellant, inclined in the direction of the first injection channel, in order to divert the flow in an improved manner, upon the flow channels entering the first injection channel in the downstream direction of the first injection channel.
A different arrangement of the flow channels may also be provided in the radial planes. Thus, the flow channels may form an angle other than zero with the radial direction, in a plane radial to the longitudinal extension of the first injection channel. In this manner, the propellant stream receives a rotational component upon entering the first injection channel. This measure may also be combined with one of the above-mentioned measures.
In another embodiment of the present invention, the third injection channel is connectable to the first propellant supply, and the first injection channel is connectable to the first propellant supply via the hydraulic connection to the third injection channel. Therefore, it is not necessary to have a separate propellant supply to the first injection channel. Rather, this is accomplished simultaneously by the hydraulically controlled connection, in particular, by the flow channels.
In addition, the second injection channel may be widened in the region of the downstream opening. This arrangement may improve the mixing of the second propellant with the adjoining streams of the first propellant.
The injection elements may include a sleeve, which surrounds the injection channels and, downstream from the injection channels, forms an annularly enclosed space into which the injection channels open. Therefore, an improved mixing of the propellants may be attained before the propellants enter into the actual reaction chamber, it being possible to adjust the mixing to corresponding requirements for it by varying the sleeve geometry, especially the size of the enclosed space.
The entire injection element may be constructed from relatively few individual elements. Thus, the injection element may be formed by a first, upstream element, a second downstream element, as well as the sleeve, which at least partially encircles the first and second elements, the first and second injection channels being formed in the first and second elements, and the third injection channel being formed between the second element and the sleeve. The individual elements are interconnected in a suitable manner. In particular, the first element is joined to the second element by a welded connection, soldered connection, or clamped connection. The sleeve may be joined to the first element and/or to the second element by a welded connection, soldered connection, or screw connection.
The individual elements and/or the sleeve may be manufactured by turning, milling, precision casting, or powder metallurgy, and the flow channels may be produced by erosive machining or boring, especially using electron-beam drilling or laser drilling.
The present invention includes an injection head, which has at least one above-described injection element. In addition, the injection head has a base plate positioned upstream and a faceplate positioned downstream, one side of the injection element being rigidly connected to the base plate, and the other side of the injection element being rigidly connected to the faceplate. Thus, a rigid connection between the faceplate and the base plate is ensured with the aid of the injection elements. This connection may also be designed in a suitable manner. In particular, the connection may be in the form of a screw connection, welded connection, or soldered connection.